This invention relates to pressure transducers for converting variations in pressure into electric signals, more specifically to semiconductor pressure converters with a silicon substrate.
These converters are so constructed that resistance regions, diode regions or transistor regions are formed in a silicon substrate and variations in the pressure applied to the substrate may be picked out as electric signals by taking advantage of the piezoelectric phenomenon or junction stress effect. In the silicon substrate used the central portion is thinned to form a diaphragm portion for facilitating distortion under a relatively low pressure, on which a subject fluid is to act. In the prior art devices a metal support with a fluid passage formed through the center thereof is used as a means for introducing the fluid into the diaphragm portion as well as for supporting the silicon substrate. For such support there is selected a metal with the coefficient of thermal expansion approximate to that of silicon so as to avoid distortion of the substrate by the difference in the coefficient of thermal expansion between the support and the silicon substrate. At present most preferred is INL Metal (trade mark, from Tokyo Shibaura) mainly composed of nickel and iron. This type of metal, however, may approximate its coefficient of thermal expansion to that of silicon only within a temperature range of about -40.degree. C. to 100.degree. C., so that the application fields for the pressure converters with such support have been limited. In order to avoid the effect of thermal distortion of the package to contain the support, a constricted portion is formed in the support in the vicinity of the portion connected to the package. However, this constricted portion alone could not fully prevent such effect, failing to ensure high-accuracy devices.